Effects of Finger Kazoo Exercise With and Without Oropharyngeal Enlargement in the Operatic Singing Voice

• Condition A (Behavioral), also known as Whitout Oropharyngeal Enlargement: Condition A consists of performing the Finger Kazoo exercise without inducing oropharyngeal enlargement. In this condition, participants place the index finger vertically in front of the lips to partially occlude the vocal tract, producing a semi-occluded vocal tract configuration, but without modifying tongue position, soft palate height, or pharyngeal wall expansion to increase the oropharyngeal space.
• Condition B (Behavioral), also known as With Oropharyngeal Enlargement: Condition B consists of performing the Finger Kazoo exercise with intentional oropharyngeal enlargement. In this condition, participants place the index finger vertically in front of the lips to partially occlude the vocal tract, producing a semi-occluded vocal tract configuration, while simultaneously modifying tongue position, elevating the soft palate, and expanding the pharyngeal walls to increase the oropharyngeal space.

Primary outcomes

• Maximum Phonation Time (MPT) variation between conditions without and with oropharyngeal enlargement. [Baseline and 48 hours after first session (allowing return to baseline before second session).]: Assessment of the difference in maximum phonation time (in seconds) between two experimental conditions: without oropharyngeal enlargement (Condition A) and with oropharyngeal enlargement (Condition B), during sustained vowel phonation. Data Collection Method: Acoustic recordings obtained using Praat software. The MPT was measured from the onset of phonation to cessation, with participants instructed to sustain the vowel at comfortable pitch and loudness. Analysis Method: Robust Paired Samples T-Test comparing MPT between Condition A and Condition B. Effect sizes calculated using Cohen's d. Results Summary: Mean MPT was significantly higher in Condition B (+7.9 s; p < .001; d = 0.46), indicating improved phonatory efficiency.

Secondary outcomes

• Change in Fundamental Frequency Stability (ΔF0) between conditions without and with oropharyngeal enlargement. [Baseline and 48 hours after first session (allowing return to baseline before second session).]: Evaluation of the mean variation in fundamental frequency (in Hz) from onset to end of sustained vowel phonation, comparing Condition A and Condition B. Data Collection Method: Praat software pitch analysis, extracting F0 mean values for initial and final 3 seconds of the sustained vowel, then calculating the difference (ΔF0). Analysis Method: Robust Paired Samples T-Test. Results Summary: ΔF0 was significantly lower in Condition B (-7.6 Hz; p < .001; d = 0.39), indicating greater pitch stability.

Other outcomes

• Change in Jitter between conditions without and with oropharyngeal enlargement. [Baseline and 48 hours after first session (allowing return to baseline before second session).]: Percentage variation in jitter between the initial and final segments of sustained vowel phonation. Data Collection Method: Jitter (%) extracted from Praat software and compared between initial and final segments. ΔJitter calculated as final - initial. Analysis Method: Robust Paired Samples T-Test. Results Summary: ΔJitter was significantly reduced in Condition B (-1.3%; p < .001; d = 0.54), indicating improved micro-frequency stability.
• Change in Shimmer between conditions without and with oropharyngeal enlargement. [Baseline and 48 hours after first session (allowing return to baseline before second session).]: Percentage variation in shimmer between the initial and final segments of sustained vowel phonation. Data Collection Method: Shimmer (%) extracted from Praat software and compared between initial and final segments. ΔShimmer calculated as final - initial. Analysis Method: Robust Paired Samples T-Test. Results Summary: ΔShimmer was significantly reduced in Condition B (-2.1%; p < .001; d = 0.57), suggesting improved amplitude stability.

Sex: All, ages: 18 Years to 55 Years, accepts healthy volunteers

Inclusion Criteria:

* Classically trained singers aged 18 to 45 years.
* Scoring below the cutoff for vocal handicap on the Singing Voice Handicap Index-10 (SVHI-10 ≤ 6 )*.
* No history of recently vocal fold pathology or laryngeal surgery.
* Non-smokers and no current upper respiratory infection.
* Willingness and ability to attend two experimental sessions spaced 48 hours apart.

Exclusion Criteria:

* Presence of any current voice disorder or history of chronic laryngeal disease.
* Recent respiratory infection within 2 weeks prior to enrollment.
* Use of medications affecting voice or respiratory function.
* Inability or unwillingness to comply with study protocol.